Digital printing technology has enabled mailers to implement digital, i.e., bit map addressable, printing in a convenient manner. It has been found to be desirable to use such techniques for the purpose of evidencing payment of postage. The computer driven printer can print, for example, a postal indicia in a desired location on the face of a mail piece.
Where it is necessary herein to distinguish such postage-meter-like devices from a typical postage meter, such devices will be called herein Postage Evidencing Devices or PED's. It should be understood, however, that the term "postage meter" as used herein will refer to both types.
Also as used herein a postal value bearing indicia will sometimes be called a Postal Revenue Block or PRB. The PRB typically contains data such as the postage value, a unique meter or PED identification number, the date and in some applications the name of the place where the mail is originating.
From the Post Office's point of view, it will be appreciated that the digital printing makes it fairly easy for someone to counterfeit a PRB since any suitable computer and printer may be used to generate multiple copies of the image.
In order to validate a mailpiece, that is to assure that accounting for the postage amount printed on a mailpiece has been properly done, it is known that one may include as a part of the franking an encrypted number such that, for instance, the value of the franking may be determined from the encryption to learn whether the value as printed on the mailpiece is correct. See, for example, U.S. Pat. Nos. 4,757,537 and 4,775,246 to Edelmann et al. as well as U.S. Pat. No. 4,649,266 to Eckert. It is also known to authenticate a mailpiece by including the address as a further part of the encryption as described in U.S. Pat. No. 4,725,718 to Sansone et al. and U.S. Pat. No. 4,743,747 to Fougere et al.
U.S. Pat. No. 5,170,044 to Pastor describes a system wherein include a binary array and the actual arrays of pixels are scanned in order to identify the provider of the mailpiece and to recover other encrypted plain text information. U.S. Pat. No. 5,142,577 to Pastor describes various alternatives to the DES encoding for encrypting a message and for comparing the decrypied postal information to the plain text information on the mailpiece.
U.K. 2,251,210A to Gilham describes a meter that contains an electronic calendar to inhibit operation of the franking machine on a periodic basis to ensure that the user conveys accounting information to the postal authorities. U.S. Pat. No. 5,008,827 to Sansone et al. describes a system for updating rates and regulation parameters at each meter via a communication network between the meter and a data center. While the meter is on-line status registers in the meter are checked and an alarm condition raised if an anomaly is detected.
While these implementations can work well, there has been no suggestion of how to implement any such concepts on a total system basis to make it practical for the large volumes of mail and large variable numbers of mailers which must be accommodated by the Postal Service.